122 



49. For these tests, pats about 1% cm. (2.95 in.) in 

 diameter, 1& cm. (0.49 in.) thick at the center, and taper- 

 ing to a thin edge, should be made, upon a clean glass 

 plate [about 10 cm. (3.94 in.) square], from cement paste 

 of normal consistency. 



50. Normal Test: A pat is immersed in water main- 

 tained as near 21 C. (70 F.)) as possible for 28 days, 

 and observed at intervals. A similar pat is maintained in 

 air at ordinary temperature and observed at intervals. 



61. Accelerated Test: A pat is exposed in any con- 

 venient way in an atmosphere of steam, above boiling 

 water, in a loosely closed vessel. 



52. To pass these tests satisfactorily, the pats should 

 remain firm and hard, and show no signs of cracking, dis- 

 tortion or disintegration. 



53. Should the pat leave the plate, distortion may be 

 detected best with a straight-edge applied to the surface 

 which was in contact with the plate. 



